1. Technical Field
The invention relates to communication systems, and more particularly, to systems that improve the intelligibility of speech.
2. Related Art
Many communication devices acquire, assimilate, and transfer speech signals. Speech signals pass from one system to another through a communication medium. All communication systems, especially wireless communication systems, suffer bandwidth limitations. In some systems, including some telephone systems, the clarity of the speech signals depend on the systems ability to pass high and low frequencies. While many low frequencies may lie in a pass band of a communication system, the system may block or attenuate high frequency signals, including the high frequency components found in some unvoiced consonants.
Some communication devices may overcome this high frequency attenuation by processing the spectrum. These systems may use a speech/silence switch and a voiced/unvoiced switch to identify and process unvoiced speech. Since transitions between voiced and unvoiced segments may be difficult to detect, some systems are not reliable and may not be used with real-time processes, especially systems susceptible to noise or reverberation. In some systems, the switches are expensive and they create artifacts that distort the perception of speech. Therefore, there is a need for a system that improves the perceptible sound of speech in a limited frequency range.